Barcelona have become stronger with Xavi, but to win La Liga is not enough, in order to prove how strong they are, for this you need to show good results in the Champions League. This year they are more fortunate with rivals in the group stage, most likely they will not have big problems to reach the playoffs together with Porto, Antwerp and Shakhtar are not the teams that can compete with Barcelona.
Actually winning La Liga tittle is seems enough prove how compete Xavi Hernandez as Barcelona head coach, they have missed with La Liga tittle almost three years and arriving Xavi can helped Barcelona winning back La Liga tittle. But still face problem when Barcelona playing in UEFA Champion League, have been two season in a row Barcelona failed for qualifying from group stage and this season time for him to make Barcelona get chance qualify to next round and winning Champion League tittles.
Current drawing group in Champion League, actually Barcelona not face difficult group what happen last season how to fight with Bayern and Inter, but in this season Barcelona looks in easy group because Porto, Antwerp and Shakhtar is not really difficult opponent for Barcelona.
I think this time Xavi has fine tuned the squad to perform well in the Champions League,I am sure he has found a place for every player and the results are showing this in the La Liga as a beginning while they are doing relatively well and I only see increase in performance for them from game to game even in difficult games like the last one against Osasuna where they won late in the second half showing character.
In Champions League they most probably will do well this time and they will pass the group stage,they have at least enough firepower to do so.Last year they didn't do well as their main objective was definitely La Liga while in this season they are fighting in two fronts.